linux-kernel - RE: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems

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Date:   Wed, 10 Jan 2018 17:38:46 +0000
From:   <Mario.Limonciello@...l.com>
To:     <rjw@...ysocki.net>, <linux-acpi@...r.kernel.org>
CC:     <andriy.shevchenko@...ux.intel.com>, <dvhart@...radead.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <valy@....ro>
Subject: RE: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems



> -----Original Message-----
> From: platform-driver-x86-owner@...r.kernel.org [mailto:platform-driver-x86-
> owner@...r.kernel.org] On Behalf Of Rafael J. Wysocki
> Sent: Wednesday, January 10, 2018 6:26 AM
> To: Linux ACPI <linux-acpi@...r.kernel.org>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>; Darren Hart
> <dvhart@...radead.org>; LKML <linux-kernel@...r.kernel.org>; Linux PM <linux-
> pm@...r.kernel.org>; Platform Driver <platform-driver-x86@...r.kernel.org>;
> Valentin Manea <valy@....ro>
> Subject: [PATCH 1/2] ACPI / PM: Use Low Power S0 Idle on more systems
> 
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Some systems don't support the ACPI_LPS0_ENTRY and ACPI_LPS0_EXIT
> functions in their Low Power S0 Idle _DSM, but still expect EC
> events to be processed in the suspend-to-idle state for power button
> wakeup (among other things) to work.  Surface Pro3 turns out to be
> one of them.
> 
> Fortunately, it still provides Low Power S0 Idle _DSM with the screen
> on/off functions supported, so modify the ACPI suspend-to-idle to use
> the Low Power S0 Idle code path for all systems supporting the
> ACPI_LPS0_ENTRY and ACPI_LPS0_EXIT or the ACPI_LPS0_SCREEN_OFF and
> ACPI_LPS0_SCREEN_ON functions in their Low Power S0 Idle _DSM.
> 
> Potentially, that will cause more systems to use suspend-to-idle by
> default, so some future corrections may be necessary if it leads
> to issues, but let it remain more straightforward for now.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=198389
> Reported-by: Valentin Manea <valy@....ro>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/sleep.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/drivers/acpi/sleep.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/sleep.c
> +++ linux-pm/drivers/acpi/sleep.c
> @@ -707,7 +707,8 @@ static const struct acpi_device_id lps0_
>  #define ACPI_LPS0_ENTRY		5
>  #define ACPI_LPS0_EXIT		6
> 
> -#define ACPI_S2IDLE_FUNC_MASK	((1 << ACPI_LPS0_ENTRY) | (1 <<
> ACPI_LPS0_EXIT))
> +#define ACPI_LPS0_SCREEN_MASK	((1 << ACPI_LPS0_SCREEN_OFF) | (1 <<
> ACPI_LPS0_SCREEN_ON))
> +#define ACPI_LPS0_S2I_MASK	((1 << ACPI_LPS0_ENTRY) | (1 << ACPI_LPS0_EXIT))
> 
>  static acpi_handle lps0_device_handle;
>  static guid_t lps0_dsm_guid;
> @@ -910,7 +911,8 @@ static int lps0_device_attach(struct acp
>  	if (out_obj && out_obj->type == ACPI_TYPE_BUFFER) {
>  		char bitmask = *(char *)out_obj->buffer.pointer;
> 
> -		if ((bitmask & ACPI_S2IDLE_FUNC_MASK) ==
> ACPI_S2IDLE_FUNC_MASK) {
> +		if ((bitmask & ACPI_LPS0_S2I_MASK) == ACPI_LPS0_S2I_MASK ||
> +		    (bitmask & ACPI_LPS0_SCREEN_MASK) ==
> ACPI_LPS0_SCREEN_MASK) {
>  			lps0_dsm_func_mask = bitmask;
>  			lps0_device_handle = adev->handle;
>  			/*

In making this change I believe you'll need to cache the values that you found from the
function mask to test them later too.
Here:
https://github.com/torvalds/linux/blob/master/drivers/acpi/sleep.c#L943

This is because later on both ACPI_LPS0_SCREEN_OFF and ACPI_LPS0_ENTRY are called
whether or not they both exist.  Fortunately looking at the DSDT in the attached bug nothing
happens if calling the undefined Arg2 == 0x05/Arg2 == 0x06 but that might not always
be the case.